1. Field of the Invention
This invention relates to an angle-adjustable hinge used for furniture with which a back is pivoted as to adjust an inclination angle of the back.
2. Description of the Related Art
The inventor of the present invention has been proposed various inventions relating to angle-adjustable hinges of this kind. For example, as shown in an assembly view of FIG. 17 and an exploded view of FIG. 18 (refer to Japanese patent No. 3766669), an angle-adjustable hinge 43 is constructed that a second arm 32 having an arc-shaped gear portion 34 of a first arm 31 forming a case portion 33 is provided, wedge-shaped window portions 35 are formed on plate piece portions 37, a floating wedge member 36 is inserted to the wedge-shaped window portions 35, the gear portion 34 of the second arm 32 and two parallel plate piece portions 38 are inserted between the two parallel plate piece portions 37 of the case portion 33, and a small pin 39 is inserted to small holes 40 and 41 to connect the first arm 31 and the second arm 32 as to oscillate around an axis 42.
The gear portion 34 has many fine gear teeth 48, the floating wedge member 36 also has fine gear teeth 49. If these gears are not certainly engaged with high dimensional accuracy, contact pressure on the gear teeth 48 and 49 becomes excessive, and cutting and rapid abrasion may be generated.
However, the angle-adjustable hinge shown in FIGS. 17 and 18 has problems described below.
(i) The gear teeth 48 of the gear portion 34 and the gear teeth 49 of the wedge member 36 engage when two independent parts (the first member 1 and the second member 2) are assembled with the small pin 39. In the assembly, dimensional errors are accumulated, contact pressure on the gear teeth 48 and 49 in use becomes high, and early abrasion and cutting of the gear teeth may be generated.
(ii) The assembly work is difficult because many small parts must be assembled as shown in FIG. 18.
(iii) The first member 1 and the second member 2 respectively have a circular pipe portion 50 formed by plastic work into a short cylinder, and use of these members assembled as in FIG. 17 is limited. That is to say, when these members are used for a chair, they are exclusively used for the chair. For other kinds of furniture, plate materials of various configurations are required for the circular pipe portion 50. Especially, when the pipe portion 50 is made plate-shaped, angled, and a bent arm, new design and production are required for each of the configurations.
(iv) Further, oscillation start angle and oscillation end angle of the first arm 31 and the second arm 32 are determined and unchanged to other angles.
(v) Therefore, for use in which another oscillation start angle and another oscillation end angle are required (use of different kind of furniture such as a sofa, a bed, a chair, etc. and different inclination conditions), different design and production are required.
(vi) It is difficult to keep the dimensional accuracy in assembled state and assembly defection may be generated because main functional parts which require high accuracy are separated into the first arm 31 and the second arm 32.
(vii) The entire load works on the small pin 39, and early abrasion and crush on the small pin 39 and the small hole 41 tend to be generated.
Therefore, it is an object of the present invention to provide an angle-adjustable hinge with which the problems (i) to (vii) described above are solved.